In this paper, we are going to study the g-natural metrics on the tangent bundle of Finslermanifolds. We concentrate on the complex and Kählerian and Hermitian structures associated with Finslermanifolds via g-natural metrics. We prove that the almost complex structure induced by this metric is acomplex structure on tangent bundle if and only if the Finsler metric is of scalar flag curvature. Then we showthat the complex structure is Hermitian if and only if the Finsler metric is of constant flag curvature.